Mosques are buildings with a unique occupancy schedule and special energy and water consumption scheme. Generally, this type of buildings lacks the application of energy efficiency solutions and sustainable guidelines during the conception, construction and the operation phase. Interestingly, these iconic edifices can play a key role in raising awareness for sustainability and promoting cleaner energy technologies. The first aim of this work is to present energy audit results, recommended energy savings solutions for two historical mosques in Marrakech (Morocco). A detailed discussion of the adopted solutions is presented and an economic assessment was performed. Then, a two-year energy savings evaluation was conducted for the two mosques. Conclusions about the adequacy of the proposed solutions is presented. The second part is dedicated to outline some guidelines and sustainable criteria to consider for establishing an international sustainable mosques label. The creation of a such sustainable label will encourage spreading sustainable best practices in mosques and other types of buildings. It will also help to compare sustainable performances of different mosques around the world by establishing an adapted sustainable rating system.